Gelcoat is the surface finish used on different types of fiberglass products.
Filon is a sheet form of fiberglass material with which many conventional construction RV's are covered. It comes in a textured as well as a gelcoat surface finish, here is a link.
Crane Co. - Filon®
However, members here primarily own molded fiberglass trailers and repair of the two materials is somewhat different. You might want to try another site for trailers of that construction such as trying a companion site.... IRV2.com.
If you Google "Filon Repair" you will also find a number of other useful links.